<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        * {
            box-sizing: border-box;
            margin: 0;
            padding: 0;
            border: 0;
        }

        body {
            width: 100vw;
            height: 100vh;
            display: flex;
            flex-direction: column;
            justify-content: center;
            align-items: center;

        }

        .box {
            width: 300px;
            border: 2px solid #ddd;

        }

        .box {
            display: flex;
            justify-content: space-evenly;
        }

        .box div:first-child {}

        .item {
            flex: 1;
            width: 150px;
            background-color: #2980B9;
            margin: 0 5px;
            display: flex;
            flex-direction: column;
            /* justify-content: center; */
            align-items: center;
            position: relative;

            text-transform: uppercase;
        }


        .item:hover ul {
            transform: scale(5);
        }

        h4 {
            width: 100%;
            height: 45px;
            display: flex;
            justify-content: center;
            align-items: center;
        }

        ul {
            list-style: none;
            position: absolute;
            top: 45px;
            left: 0px;
            background-color: #2980B9;
            transform: scale(0);
            padding: 20px;
            transition: 1s;
            transform-origin: top left;
        }
    </style>
</head>

<body>
    <div class="box">
        <div class="item">
            <h4> 首页</h4>
            <ul>
                <li>css</li>
                <li>css</li>
                <li>css</li>
            </ul>

        </div>
        <div class="item">
            <h4> 功能</h4>
            <ul>
                <li>js</li>
                <li>js</li>
                <li>js</li>
            </ul>
        </div>
    </div>
</body>

</html>